Protective atmosphere for sheet glass casting rolls



1966 L. A. B PXLKINGTON 3,231,354

PROTECTIVE ATMOSPHERE FOR SHEET GLASS CASTING ROLLS Original Filed June'7, 1957 I rwentor United States Patent Originalapplicationdune 7,1957;Ser. No.'664,245, now

Patent No. 3,083,551,-dated -Apr. 2, 1963. Divided 'andthisaapplicationDec. '27 1961', Ser. No. 162,450

- Claims priority, application Great'Britaim'May 3, 1957,

t ,205 3.Claims. (Cl. 65-157) This invention relates to the manufactureofflat glass and is a division from copending application Serial No.

664,245, filed June. 7, 1957, Patent No. 3,083,551.

In the. aforesaid copending application there isdisclosed and claimedapparatus for producing flat glass on a support in the form of a bath ofmolten metal. The invention described in the aforesaidcopending-application comprises conventional rolling means fordelivering a ribbon of glass at a controlled rate onto the supportconstitutedby the bath of molten metaland advancing the glass on thesupport under thermal conditions which transform the ribbon into a layerof molten glass while ensuring unhindered lateral flow of the side edgesof the layer to the limit of its free flow under the influence of "theforces of surface tension and gravity.

In accordance with the present invention the conventional casting rollsoperate in an enclosure in which enclosure a protecting atmosphere'forthe casting rolls is maintained at a plenum. The protecting atmospheremay be a reducing gas or a gas inert to the metal from which the castingrolls are manufactured. If a reducing atmosphere is employed it .isconvenient to supply. to the enclosure commercial coal gas. .Bymaintaining a plenum within the enclosure ingress of ambient atmospheresinto the enclosure is prevented.

Accordingly the present invention comprises apparatus for rolling moltenglass into ribbon form wherein the casting rolls, to which the-moltenglass is fed and bytnem converted into ribbon form as the molten massenters the pass between them, are housed in an enclosure erected aboutthe rolls and means are provided for maintaining at a plenum within theenclosure a protecting atmosphere to ensure that ingress into theenclosure of ambient atmospheres is prevented.

In one preferred form of apparatus according to the invention theapparatus comprises in combination within an enclosure metal castingrolls, regulatable means for delivering molten glass to the pass betweenthe casting rolls, supporting means for carrying the ribbon of glass asit is advanced by the casting rolls, an end wall to the enclosure on thedischarge side of the casting rolls, set with respect to the supportingmeans for the glass to permit the advance of the ribbon on the support,and means for supplying a protecting atmosphere for the casting rollsinto the enclosure.

Such apparatus may comprise in accordance with the present invention aspout for delivering molten glass to the pass between the casting rolls,and characterised in that the supporting means for the ribbon of glassis a molten bath, said molten bath being confined in a tank structurecomprising side walls, end walls and a floor, the side walls and thefloor being integral each with the others, one end wall being disposedin contiguity with the spout, said side walls and the tank structuresupporting the enclosure.

In order that the invention may be more clearly understood a preferredembodiment will now be described with reference to the accompanyingdiagrammatic drawings.

In the drawings FIGURES 1 and 2 are a sectional eleva- "ice tion'andplan respectively-- of rolling means for converting molten glassinto aribbon of glass in association-with supporting means, for the glassribbon produced, in the form'of abathofmolten metal.

In the drawings like references J designate the same 1 parts.

F Intheconstruction showninFIGURES' 1" and 2 there is illustrated-aforehearth of a continuous. glass melting I tank indicated. at 1, aregulatingtweelat 2-: anda spoutfi,

the spout comprisingafloor or lip 4 and side jarnbs S one of which onlyis illustratedin-"FIGURE l, the side jambsand lip forming a spout ofgenerally rectangular cross section. A cover may be secured overthespout.

- Operativelyassociatedtwith the-spout .are. a .pairzof water-cooledcasting rolls indicated at 6 and 7, and these rolls arenmounted on:frames 8, 18. in usualmannenand driven through. two tooth. wheels. 9,. 9by. power means.

A gate 10 isadjustably suspendedin known manner '(by means notshown) ina vertical planein contiguity with theupper casting roll 6. The gate 10.shields :the .top .roll 6 from the heat radiated by the molten glass11.,flowing from the: forehearth over .thejlip :4:.to the. pass. betweenJ the rolls 6, 7.

Theupper casting roll 6v is. disposed .in advance of the lower castingroll 7 so that the, molten glass llfiows from .thelipA-onto anupper partof the roll 7- presenting to the 2 glass. a downwardly and;forwardlydirected arcuate casting bed moving in thesame sense asthedirection; of the fiow from the spout, thus the moltenglasson'leaving the spout and arriving on this casting bed isconstrained to :fiow forwardly, thereby; preventing backward flow. ofthe -;molten glass leaving the spout4.

-.The conventional ribbonforming means, just described, is in the,construction illustrated, disposed over the floor 12 of a tank structureincluding also side walls 13 joined together at eachend of the tankstructureby end walls 14 -only'one. ofwhich is shown in FIGURE 1,saidside walls being integral with the-floor and end walls.

The tankstructure-is.usedtoconfinea molten :bath

. 15.having the characteristic-set out in the aforesaid Patent No.3,083,551, the level of the surface of which bath is indicated at 15 ofFIGURE 1. The surface of the molten bath acts as a support for theribbon of glass 23, produced by the action of the casting rolls 6, 7, onthe molten glass fed to the pass between them, which ribbon is advancedby the casting rolls, as it is formed, along the bath which latterbecause it has a higher specific gravity than the glass supports theribbon 23 in a horizontal plane.

It will be seen that the end wall 14 of the tank structure meets theunder-surface of the spout 3 and that the lower casting roll is inproximity to the end wall 14 of the tank structure.

The tank structure supports a roof structure including a roof 17 and avertically adjustable end wall at each end of the roof structure, theadjustable end wall nearer the casting rolls is indicated at 18 inFIGURE 1 the other end wall is not shown, but is fully described in theaforesaid Patent No. 3,083,551. The roof structure provides a tunnelover the bath 15 and defines a headspace 20 thereover.

The adjustable end wall 18 of the roof structure forms part of anenclosure for the casting rolls the ceiling and side walls of which areindicated at 25 and 26 respectively, the side walls being carried by theside Walls 13 of the tank structure and the ceiling 25 being extendedback to the regulating gate 10.

Thermal regulators 28 and 29 within the tank structure and roofstructure respectively, maintain the temperature required in the moltenbath and in the headspace over the bath, requisite for carrying out themethod of production as described in the aforesaid patent.

As fully described in the aforesaid patent a protecting atmosphere ismaintained at a plenum in the head space 20 over the bath 15, theprotecting atmosphere being .supplied through a series of ducts 39connected by branches 40 to headers 41. The presence of this protectingatmosphere over the molten bath prevents chemical reactions occurring atthe surface of the bath and the passage of the protecting gases underthe end wall 18 of the roof structure into the enclosure housing therolls 6, 7 and comprising the ceiling 25, side walls 26, and end wall18,-ensures that the rolls 6, 7 operate in that atmosphere whichenvelopes them thereby protecting the rolls from corrosion on theirsurfaces.

Ordinary commercial coal gas can be supplied through ducting 39 toprovide the protecting atmosphere and the existence of a plenum in theenclosure ensures that ingress into the enclosure of ambient atmospheresis prevented.

Instead of delivering the protecting gas into the enclosure by ensuringpas-sage under the end wall 18, the protecting gas may be admitteddirectly into the chamber by piping not shown, which piping may besupplied from the same source of protecting gas as that supplied to theheaders 41.

As is well known in the manufacture of flat glass by the conventionalrolling methods all imperfections on the roller surfaces are imparted tothe surfaces of the ribbon of glass produced by them and involveextensive mechanical surfacing operations on the glass in the productionof a marketable commodity. By providing the protecting gas about therolls the existence of such imperfections is considerably reduced. 7

I claim:

1. Apparatus for rolling molten glass into ribbon form comprising, incombination, a pair of casting rolls between which the molten glass ispassed and by them converted into ribbon form, said rolls having glasscontacting surfaces subject to corrosion, a housing which forms a headspace over the casting rolls,.and means for maintaining within thehousing a protecting atmosphere which pro vents ingress of ambientatmosphere. 7

2. Apparatus for rolling molten glass into ribbon form comprising, incombination, a pair of casting rolls between which the molten glass ispassed and by them converted into ribbon form, said rolls having glasscontacting surfaces subject to corrosion, a bath of molten metal ontowhich the glass ribbon is delivered by the casting rolls, a housingwhich forms a head space over the casting rolls, said housing having anend wall on the discharge side of the rolls set in spaced relation tothe surface of the molten metal bath to permit the glass ribbon to beadvanced along the bath under the end wall, and means for maintatiningwithin the housing a protecting atmosphere which prevents ingress ofambient atmosphere.

3. Apparatus for rolling molten glass into ribbon form comprising, incombination, a pair of casting. rolls between which the molten glass ispassed and by them converted into ribbon form, said rolls having glasscontacting surf-aces subject to corrosion, a bath of molten metal ontowhich the glass ribbon is delivered by the casting rolls, a tankstructure containing said molten metal bath and within which the castingrolls are mounted at the inlet end thereof, means defining a' head spaceover the molten metal bath and the casting rolls, a wall in the headspace on the discharge side of the casting rolls set in spaced relationto the surface of the molten metal bath to permit the glass ribbon to beadvanced along the bath under the wall, and means for maintaining in thehead space over the molten metal bath and the casting rolls a plenum ofprotecting gas which prevents the ingress of ambient atmosphere intosaid head space, the setting of the wall with respect to the ribbonpassing thereunder permitting flow of the protecting gas from the headspace over the molten metal bath into the head space over the castingrolls.

References Cited by the Examiner 2,911,759 11/1959 Pilkington et a1.65--157 X DONALL H. SYLVESTER, Primary Examiner.

D. CRUPAIN, Assistant Examiner.

1. APPARATUS FOR ROLLING MOLTEN GLASS INTO RIBBON FORM COMPRISING, IN COMBINATION A PAIR OF CASTING ROLLS BETWEEN WHICH THE MOLTEN GLASS IS PASSED AND BY THEM CONVERTED INTO RIBBON FORM, SAID ROLLS HAVING GLASS CONTRACTING SURFACES SUBJECT TO CORROSION, A HOUSING WHICH FORMS A HEAD SPACE OVER THE CASTING ROLLS, AND MEANS FOR MAINTAINING WITHIN THE HOUSING A PROTECTING ATMOSPHERE WHICH PREVENTS INGRESS OF AMBIENT ATMOSPHERE. 